Wheel bearing for a driven rigid axle

ABSTRACT

A wheel bearing for a driven rigid axle, having a drive shaft includes a rolling bearing unit which comprises at least one inner race and at least one outer race, an inner race which is oriented toward the outside of the vehicle being designed with an end flange aligned in this direction, and further includes at least along a partial region of its length, a hub profile of a shaft-hub connection, the hub profile being connected to a complementary profile arranged on the drive shaft, an axle body which is mounted in a rotationally fixed manner on the vehicle body, radially surrounds the drive shaft at least along a partial region of its length and forms or accommodates an outer race of the rolling bearing unit, a wheel flange which accommodates at least one drive wheel, and a brake disk which comprises a friction ring and a brake-disk chamber, the brake disk being releasably fastened together with the wheel flange to the end flange of the inner race. In the wheel bearing, the brake disk can be removed without detaching the bearing.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a U.S. national phase of International PatentApplication No. PCT/EP02/04844, filed May 3, 2002, designating theUnited States of America, and published in German as WO 02/100663 A1,the entire disclosure of which is incorporated herein by reference.Priority is claimed based on German Patent Application No. 101 28 073.4,filed Jun. 9, 2001.

BACKGROUND AND SUMMARY OF THE INVENTION

The invention relates to a wheel bearing for a driven rigid axle, havinga drive shaft which is mounted in or on an axle body.

Elements of this invention are disclosed in DE 197 44 871 A1. A rollingbearing, for example of a multi-link axle, bears axially with its innerrace against a shaft shoulder of the drive shaft while the outer race ispressed into an axle stub. The brake disk, which has a wheel-supportingsurface, sits with a serrated profile on a corresponding mating profileof the drive shaft. With the aid of a central screw on the drive shaft,the brake disk is clamped against the rolling bearing and the latter isclamped against the shaft shoulder of the drive shaft. Including thethread, there are five settlement joints in this case.

If the brake disk is removed, the central fastening screw has to beundone. In the process, the inner race of the rolling bearing can bereleased from bearing against the shaft shoulder. After installation of,for example, a new brake disk, the central screw is tightened again.

There is the risk here of the rolling bearing being prevented, forexample because of fretting corrosion, from reaching its originalposition on the shaft shoulder. This may lead to the joints of theconnection settling, which may cause a reduction in the prestressingforce.

The transverse and longitudinal forces acting on the wheel during thedriving mode act directly as an alternating stress on the wheel-bearingfastening and can thus further loosen the wheel fastening.

The problem on which the present invention is based is therefore todevelop a wheel bearing for a driven rigid axle, in which it is possibleto remove a brake disk without releasing the wheel bearing.

This problem is solved by the features of the invention described andclaimed herein. For this purpose, the wheel bearing is provided with arolling bearing unit which comprises at least one inner race and atleast one outer race, an inner race which is oriented toward the outsideof the vehicle being designed with an end flange aligned in thisdirection and having, at least along a partial region of its length, ahub profile of a shaft-hub connection, the hub profile being connectedto a complementary profile arranged on the drive shaft, having an axlebody which is mounted in a rotationally fixed manner on the vehiclebody, radially surrounds the drive shaft at least along a partial regionof its length and forms or accommodates an outer race of the rollingbearing unit, having a wheel flange which accommodates at least onedrive wheel, and having a brake disk which comprises a friction ring anda brake-disk chamber, the brake disk being releasably fastened togetherwith the wheel flange to the end flange of the inner race.

In order to remove the brake disk, the releasable connection, with whichthe brake disk and the wheel flange are fastened to the inner race ofthe rolling bearing unit, is released. In the meantime, the rollingbearing unit can be fixed axially and/or radially. In order to changethe brake disk, the latter is removed together with the wheel flange. Anew brake disk is then fitted in turn together with the wheel flange andfastened releasably to the inner race of the rolling bearing unit. Onlythis connection has to be released and fastened again in order to changethe brake disk. No additional components are released or loosened in theprocess. Including the thread, there are at most four settlement jointsin the fastening of the releasable connection.

The torque from the drive shaft is transmitted via a form-fittingshaft-hub connection to the inner race of the rolling bearing unit. Viathe end flange on the inner race of the rolling bearing unit, the torqueis passed on further via the frictional flange connections between theinner race and the brake disk and between the brake disk and the wheelflange to the wheel flange and from there to the wheels. The wheelflange may also be part of the brake disk. In this case, a drivingtorque from the inner race is transmitted via a frictional connection tothe brake disk and is passed on from there directly to the wheel flange.

A braking torque is transmitted by the brake disk to the wheel flange.If a brake disk is integrated in the wheel flange, the braking torque ispassed directly from the brake disk into the wheel flange. If the brakedisk and the wheel flange are separate components, the transmission ofthe braking torque takes place, for example, via a frictional and/orform-fitting connection between the brake disk and the wheel flange.

The brake disk can be centered during installation and can be fittedsimply and securely.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a wheel bearing for a driven rigid axle.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the wheel bearing for a driven rigid axle, for example arear axle with dual tyres for a commercial vehicle. The individualdriven wheel (not illustrated here) is mounted via a rolling bearingunit (10) on an axle body (60), which, as a rule, is supportedresiliently on the vehicle body. A shaft (30) driving the driven wheelis arranged in the hollow axle body (60). In this case, the drive shaft(30) is connected to a differential housing (not illustrated here).

The rolling bearing unit (10) comprises, inter alia, an inner race (12)rotating with the drive shaft (30) and an outer race (11) arranged inthe axle body (60). In its region oriented toward the outside of thevehicle, the inner race (12) is connected to the drive shaft (30) via ashaft-hub connection (34, 19).

A brake disk (40) and a wheel flange (45) are fastened to a flange (17)at the end of the inner race (12) by means of hub screws (2). The brakedisk (40) comprises, inter alia, a friction ring (52) and a brake-diskchamber (42). The rims (not illustrated here) of the wheels are fastenedreleasably to the wheel flange (45).

A sealing element (70) is arranged between the axle body (60) and thedrive shaft (30). Said sealing element seals a cavity (1) between thedrive shaft (30) and the axle body (60), the cavity being connected tothe interior of the differential housing.

The drive shaft (30) is divided into three regions. At both of its ends,the drive shaft (30) bears profiles, on the shaft side, of a shaft-hubconnection while the central region is of at least approximatelycylindrical design. A central threaded hole (33) is arranged on its endside which is oriented toward the outside of the vehicle.

The profile on the shaft side (not illustrated in FIG. 1) is used toconnect the drive shaft (30) in a form-fitting manner to the outlet fromthe differential housing. In the first region, the drive shaft (30) isdesigned, for example, as a splined shaft profile. Instead of a splinedshaft profile, use may also be made of a serrated profile, a polygonalprofile, etc. In this region of the drive shaft (30), the outsidediameter is at least 5% larger than in the central region. At least theouter end of the splined shaft profile can be beveled, for example, atan angle of 15°–25° with respect to the horizontal.

The second, central and cylindrical region of the drive shaft (30) has avirtually constant diameter. A cylindrical subsection (36) can have, forexample, a small surface roughness, for example with a peak-to-valleyheight R_(t) of between 1 and 4 μm. In this subsection (36), at leastthe surface of the drive shaft (30) can have a hardness of, for example,45–60 HRC.

In the third region of the drive shaft (30), which region is orientedtoward the outside of the vehicle, the outside diameter of the driveshaft (30) is smaller than in the central region. The profile (34),which is on the shaft side, of this shaft-hub connection may be asplined shaft profile, for example. It then has, for example, 20 splineson the circumference of the shaft section, a spline having two parallelflanks in each case. Between the splines (35) the diameter of the driveshaft is, for example, approximately 10% smaller than the outercircumference. It is also possible in this case for the profile (34), onthe shaft side, of the shaft-hub connection to be a serrated profile, apolygonal profile, etc.

The rolling bearing unit (10) mounted on the drive shaft (30) is, forexample, a tapered roller bearing in two rows with an O-arrangement. Itcomprises two inner races (12, 22) and an outer race (11) between whichthe rolling bodies (13) are arranged. The inner race (12), which istubular in some regions, is designed as a flange (17) at its outwardlyoriented end. The flange (17) extends radially outward in this case. Aplurality of continuous threaded holes (18) are arranged on a graduatedcircle therein.

The inner surface of the inner race (12) is divided into two regions ofdifferent diameter. A first region in the vicinity of the flange (17) isapproximately the same length as the splined shaft profile (34) of thedrive shaft (30). The hub profile (19), the mating profile of thesplined shaft profile (34) of the drive shaft (30), is arranged in thehole of this region. The grooves, for example 20 grooves, are the widthof the splines (35) of the splined shaft profile (34) and are centeredon their flanks. The inside diameter of the hub profile (19) isapproximately 10% smaller than the outside diameter of the splined shaftprofile (34).

The hub profile (19) peters out toward the center of the vehicle into anundercut which is adjoined by the second region (15) of the innersurface of the inner race (12). This second region (15) is hollowcylindrical and is approximately the length of the outer race (11) ofthe rolling bearing unit (10). The inner race uses this region (15) tosit on the cylindrical region of the drive shaft (30).

A rolling bearing track (14) is arranged on the outside of the innerrace (12) via the cylindrical region (15) of the inner surface. Acylindrical region and a thread (16) adjoin the inner race (12) towardthe center of the vehicle after an intermediate section.

A second inner race (22) is arranged on the cylindrical region. Thisinner race also has a rolling bearing track (23) on its outer surface.The bearing clearance of the rolling bodies (13) is set via this innerrace (22) with the aid of a setting nut (24) fitted on the thread (16).

The outer race (11) of the rolling bearing unit (10) includes tworunning tracks for the rolling bodies (13) on its inside. The outside ofthe outer race (11) is cylindrical.

Instead of in an O-arrangement, the bearing unit (10) may also bearranged in an X-arrangement. In this case, for example, the outer race(11) of the bearing unit (10) is divided. The bearing clearance is thenset at the outer race (11).

The axle body (60), which may also be part of a steerable axle, is atube which is open at its ends and has an outside diameter which iscylindrical at least in some regions. The inner surface (65) of the axlebody (60) is divided into a plurality of regions of different diameter,the common central line of which coincides with the axis of rotation(8), and which lie concentrically with respect to the outer surface ofthe axle body (60).

A bearing seat (62) is arranged in the first region, at that free end ofthe axle body (60) which faces away from the fastening to the vehicle.Said bearing seat is bounded toward the center of the vehicle by an axlebody shoulder (63) and toward the free end by a thread (64). The outerrace (11) of the tapered rolling bearing (10), which is in two rows, issupported on the bearing seat (62). The outer race (11) is clampedagainst the axle body shoulder (63) via a torsionally secured supportingwasher (6) with the aid of a securable hub nut (5). In this case, thehub nut (5) may have a shaft sealing ring (7) which bears against theinner race (12).

The sealing element (70) is arranged in a further region (67) of theinner surface (65). In this region (67), the diameter of the innersurface (65) is approximately two thirds of the diameter of the bearingseat (62).

In the case of a rolling bearing unit (10) in an X-arrangement, forexample, the axle body (60) may also form an outer race of the rollingbearing unit. A rolling bearing track (14) for the rolling bodies (13)is then arranged on the inner surface of said outer race. The rollingbearing unit (10) may also be designed in the form of a single row or asa pre-set bearing.

The brake-disk chamber (42) is arranged around the axle body (60). Saidchamber has a cylindrical inner and outer contour. In this case, theoutside diameter of the brake-disk chamber (42) is approximately 15–25%larger than its inside diameter. It has a fastening flange (43) at itsend oriented toward the outside of the wheel. Said fastening flange isoriented perpendicular with respect to the axis of rotation (8) of thewheel and comprises two mutually parallel and flat sides. Holes (44) inalignment with the threaded holes (18) of the inner race (12) arearranged on this fastening flange (43).

A friction ring (52) is arranged on the outer surface of the brake-diskchamber (42), at its end which is oriented toward the center of thevehicle. An assembly joint can be arranged in the transition point (51),the “shielding”.

The friction ring (52) may be connected non-releasably or releasably tothe brake-disk chamber (42). In the case of a releasable connection,this can be, for example, a form-fitting shaft-hub connection in theform of a multi-groove profile, a serrated profile, etc.

The parallel outer surfaces of the friction ring (52) form the frictionsurfaces (53) against which the brake linings bear during braking. Theoutside diameter of the friction ring (52) is, for example,approximately 75% larger than the outside diameter of the outer surfaceof the brake-disk chamber (42).

The wheel flange (45) sits on the outer contour of the brake-diskchamber (42). In this case, the wheel flange (45) is arrangedapproximately over half of the entire length of the brake-disk chamber(42) and is centered on the latter. The wheel flange (45) merges towardthe outside of the vehicle into a wheel-flange chamber (48). Thiswheel-flange chamber (48) has a cylindrical outer surface at least insome regions and, at its end side, a fastening flange (49) with passageholes (56) which lie on a graduated circle. In the fitted state, thepassage holes (56) of the wheel flange (45) lie over the passage holes(44) of the brake-disk chamber (42) and the threaded holes (18) of theinner race (12). The hub screws (2) are then inserted into the holes(18) and tightened with a prestressing force.

The outside diameter of the wheel flange (45) is approximately one and ahalf times as large as the diameter of the wheel-flange chamber (48). Onits side oriented toward the outside of the wheel, the wheel flange (45)has a wheel-supporting surface (46). The latter is a flat, machinedannular surface which is arranged perpendicular with respect to the axisof rotation (8) of the wheel. The maximum diameter of thewheel-supporting surface (46) corresponds to the maximum outsidediameter of the wheel flange (45), and the inside diameter correspondsapproximately to the diameter of the wheel-flange chamber (48). In thiscase, the usable minimum inside diameter of a friction surface (53) ofthe friction ring (52) is smaller than the maximum outside diameter ofthe wheel-supporting surface (46) on the wheel flange (45). A releasenotch is arranged between the machined wheel-supporting surface (46) andthe cylindrical section of the outer surface of the wheel-flange chamber(48). The wheel-supporting surface (46) is part of a plane which cutsapproximately centrally across the bearing (10). Parallel to the axis ofrotation (8) of the wheel, passage holes (47) are arranged on agraduated circle in the wheel-supporting surface (46). The fasteningmeans for fastening the rims are arranged in these holes (47). That endsurface of the wheel flange (45) which is oriented toward the inside ofthe wheel is parallel to the wheel-supporting surface (46). This surfaceis likewise an annular surface, but its inside diameter is approximately10% larger than the inside diameter of the wheel-supporting surface(46).

The arrangement of the wheel flange (45) on the brake-disk chamber (42)causes forces from the wheel flange (45) to be introduced into theradial outer side of the brake-disk chamber (42).

A securing washer (4) and a plain washer (3), for example in the form ofa disk spring, are arranged on the end side (32) of the drive shaft(30). Both washers have a central hole. A fastening screw (9), thethread of which is screwed into the threaded hole (33), fastens the twowashers (3, 4) on the drive shaft (30). In this case, the outer edge ofthe securing washer (4) presses against the inner race (12) of therolling bearing unit (10). On its side oriented toward the outside ofthe vehicle, the disk spring (3) bears against the inside of thefastening flange (49) of the wheel flange (45). This secures the driveshaft (30) against axial displacement. This connection is not undone forthe purpose of removing the brake disk (40).

The sealing element (70) is arranged between the rolling bearing unit(10) and the differential housing. Said sealing element is of annularconstruction and bears with its outside against the second section (67)of the inner surface (65) of the axle body (60) while its inside, forexample, touches the subsection (36) of the drive shaft (30). The lengthof the sealing element (70) corresponds approximately to double thedifference of the hole diameter of the axle body (60) and of the outsidediameter of the drive shaft (30) in the region of the sealing element(30). In other words, the height of the sealing element (70) is smallerthan one third of its length.

The sealing element (70) is of c-shaped construction in cross-section,the inner and the outer limbs of the C being approximately the samelength and being situated approximately one above the other. In thiscase, the opening of the C points in the direction of the differentialhousing. The sealing element (70) therefore bounds the cavity (1) whichcommunicates with the interior of the differential housing. The sealingelement (70) comprises an elastomer body (71), which consists, interalia, of an outer casing (72), a bottom casing (73) and a membrane (74).The length of the coiling of the elastomer body (71) correspondsapproximately to four times the difference between the inside diameterof the axle body (60) and the outside diameter of the drive shaft (30).

Before the rolling bearing unit (10) is installed, first of all, forexample, the securable hub nut (5) is pushed together with the shaftsealing ring (7) onto the inner race (12). After the rolling bodies(13), which are oriented toward the outside of the wheel, are installedon the rolling bearing track (14) of the inner race (12), the outer race(11) is inserted. After that, the second row of rolling bodies (13) andthe second inner race (22) are inserted. The clearance in the rollingbearing unit (10) can then be set with the aid of the securing nut (24),which can be secured if appropriate.

The rolling bearing unit (10) preassembled in this manner is theninserted into the space between the drive shaft (30) and the axle body(60). If appropriate, one of the two bearing seats in this case has apress fit. In this connection, the shaft sealing ring (7) may supportthe hub nut (5) on the inner race (12). During installation, thetightening of the hub nut (5), for example with the aid of a hookwrench, in the thread (64) of the axle body (60) causes the outer race(11) of the rolling bearing unit (10) to be pressed the rolling bearingunit (10) against the axle body shoulder (63) and to be secured in theaxle body (60).

During installation of the rolling bearing unit (10), the shaft-sideprofile (34) of the drive shaft (30) come into engagement in aform-fitting manner with the hub-side profile (19) of the inner race(12). In this case, the respective flanks are placed against each other,for example in a splined shaft connection.

After installation of the axial securing means (3, 4, 9), the brake disk(40) and the wheel flange (45) are fitted and fastened by the hub screws(2).

In order to remove the brake disk (40), the hub screws (2) are undone.The fastening screw (9) is not removed. The brake disk (40) and thewheel flange (45) can then be removed together or separately.

If a new brake disk (40) is fitted, the latter is fastened together withthe wheel flange (45) to the inner race (12). The brake disk (40) iscentered here on the outer surface of the inner race (12). The hubscrews (2) secure the frictional connection between the brake disk (40)together with the wheel flange (45) and the inner race (12).

The foregoing description and examples have been set forth merely toillustrate the invention and are not intended to be limiting. Sincemodifications of the described embodiments incorporating the spirit andsubstance of the invention may occur to persons skilled in the art, theinvention should be construed broadly to include all variations fallingwithin the scope of the appended claims and equivalents thereof.

1. A wheel bearing for a driven rigid axle, comprising: a drive shaft, arolling bearing unit which comprises at least one inner race and atleast one outer race, an inner race which is oriented in a directiontoward an outside end of the axle being designed with an end flangealigned in the outside direction and, at least along a partial region ofits length, a hub profile of a shaft-hub connection, the hub profilebeing connected to a complementary profile arranged on the drive shaft,an axle body which is arranged to be mounted in a rotationally fixedmanner on a vehicle body, radially surrounds the drive shaft at leastalong a partial region of its length and forms or accommodates an outerrace of the rolling bearing unit, a wheel flange which accommodates atleast one drive wheel, and a brake disk which comprises a friction ringand a brake-disk chamber, brake disk being releasably fastened togetherwith the wheel flange to the end flange of the inner race.
 2. The wheelbearing as claimed in claim 1, wherein the wheel bearing unit is in tworows.
 3. The wheel bearing as claimed in claim 1, wherein the smallestusable diameter of the friction ring is smaller than the smallestdiameter of the wheel-supporting surface.
 4. The wheel bearing asclaimed in claim 1, wherein the wheel flange is arranged on the outercontour of the brake-disk chamber.
 5. The wheel bearing as claimed inclaim 1, wherein the wheel flange introduces force on the radial outerside of the brake-disk chamber.
 6. The wheel bearing as claimed in claim1, wherein at least one sealing element is arranged between the axlebody and the drive shaft, said sealing element sealing a cavity which issituated between the drive shaft and the axle body and communicates withthe interior of a differential housing.
 7. The wheel bearing as claimedin claim 1, wherein at least one frictional, releasable connection isarranged between the inner race and the wheel flange.
 8. A wheel bearingfor a driven rigid axle of a vehicle, comprising: a drive shaft, arolling bearing unit which comprises an inner race and an outer race,wherein the inner race includes an end flange facing away from thevehicle and includes a hub, wherein the hub is connected to acomplementary profile on the drive shaft, an axle body that is arrangedto be mounted in a rotationally fixed manner on the vehicle's body,wherein the axle body at least partially surrounds the drive shaft andincludes or contains an outer race of the rolling bearing unit, a wheelflange for attachment of a drive wheel, and a brake disk which includesa friction ring and a brake-disk chamber, the brake disk beingreleasably fastened to the wheel flange and to an end flange of theinner race.
 9. The wheel bearing as claimed in claim 8, wherein thewheel bearing unit includes two rows.
 10. The wheel bearing as claimedin claim 8, wherein the wheel flange includes a wheel-supportingsurface, and wherein a smallest usable diameter of the friction ring issmaller than a smallest diameter of the wheel-supporting surface. 11.The wheel bearing as claimed in claim 8, wherein the wheel flange isarranged on an outer contour of the brake-disk chamber.
 12. The wheelbearing as claimed in claim 8, wherein the wheel flange introduces forceon a radial outer side of the brake-disk chamber.
 13. The wheel bearingas claimed in claim 8, further comprising at least one sealing elementthat is arranged between the axle body and the drive shaft, the sealingelement sealing a cavity that is between the drive shaft and the axlebody and communicates with an interior of a differential housing. 14.The wheel bearing as claimed in claim 8, further comprising at least onefrictional, releasable connection between the inner race and the wheelflange.